C++的Windows.h有哪些实用函数？

Windows.h里基本上直接或间接包含了所有Windows常用的API. 维基百科 上抄来了一个列表

• excpt.h – Exception handling
• stdarg.h – variable-argument functions (standard C header)
• windef.h – various macros and types
• winnt.h – various macros and types (for Windows NT )
• basetsd.h – various types
• guiddef.h – the GUID type
• ctype.h – character classification (standard C header)
• string.h – strings and buffers (standard C header)
• winbase.h – kernel32.dll : kernel services; advapi32.dll :kernel services(e.g. CreateProcessAsUser function), access control(e.g. AdjustTokenGroups function).
• winerror.h – Windows error codes
• wingdi.h – GDI (Graphics Device Interface)
• winuser.h – user32.dll : user services
• winnls.h – NLS (Native Language Support)
• wincon.h – console services
• winver.h – version information
• winreg.h – Windows registry
• winnetwk.h – WNet (Windows Networking)
• winsvc.h – Windows services and the SCM (Service Control Manager)
• imm.h – IME (Input Method Editor)

上述头文件都是被Windows.h间接包含的。

至于实用的函数，那就要看你如何定义“实用”了。这里就不讨论了。